Weakly Interacting Bose Mixtures at Finite Temperature

TL;DR

This paper investigates finite-temperature weakly interacting Bose mixtures, revealing unique effects such as the absence of pure phases and the coexistence of condensates without mixing, using Hartree-Fock theory to produce experimentally relevant phase diagrams.

Contribution

It provides the first detailed phase diagrams for finite-temperature Bose mixtures with tunable interactions, highlighting effects absent at zero temperature.

Findings

No pure phases exist at finite temperature.

Condensates of both species can coexist without mixing.

Phase diagrams are applicable to trapped experimental systems.

Abstract

Motivated by the recent experiments on Bose-Einstein mixtures with tunable interactions we study repulsive weakly interacting Bose mixtures at finite temperature. We obtain phase diagrams using Hartree-Fock theory which are directly applicable to experimentally trapped systems. Almost all features of the diagrams can be characterized using simple physical insights. Our work reveals two surprising effects which are dissimilar to a system at zero temperature. First of all, no pure phases exist, that is, at each point in the trap, particles of both species are always present. Second, even for very weak interspecies repulsion when full mixing is expected, condensate particles of both species may be present in a trap without them being mixed.